Most of the IPMI Systems out there still using good old Java based Remote Applications to connect to the remote console.
Sine Java 8 update 111, the MD5 singing algorithm was marked as insecure (aka disabled) by Oracale (see Relase Notes for that Release ” Restrict JARs signed with weak algorithms and keys”).
You will get an “Security Error while using MD5withRSA Signature”:

The only solution to fix this error is to have your Hardware Vendor to update the IPMI Firmware with JARs, signed with a more up to date singing algorithm. A work around is to re-enable MD5 for the time being. For that you need to get into your Browser Java Installation.
On my Mac this is in

/Library/Internet Plug-Ins/JavaAppletPlugin.plugin/Contents/Home

You need to edit lib/security/java.security and remove MD5 from jdk.jar.disabledAlgorithms.